Nowadays, thermostating or constant temperature control in automatic main-flow biochemical analyzers is performed mainly in three ways: air bath (air dry bath), water bath/thermostating liquid bath, and solid-solid direct-heating (thermostating by direct contact between solid objects). By adopting an air bath thermostat, a simple structure can be provided, the system temperature can be increased or decreased in a moderate speed, and no maintenance is needed. However, air bath thermostats suffer from that the temperature is likely to be affected by the environment and is thus unstable, and the increasing and decreasing of the liquid in the reaction cups are slow. Water bath/thermostating liquid bath has the advantage that the temperature is even and stable as well as the disadvantages that the increasing and decreasing speeds of the system temperature are low, the preheating time in the start-up stage is long, and the quality of water may be changed (such as microorganism growth and mineral substance deposition) which may affect the photo sensing in the optical path of the system and thus needs a frequent maintenance. In a system adopting a solid-solid direct-heating thermostat, the temperature of the liquid in the reaction cups can be increased and decreased quickly, and the temperature can be kept stable and even.
In known solid-solid direct-heating structures, there is a reaction disc body composed of, among other components, a bottom plate, a main plate and five reaction cup clampers. The main plate and the reaction cup clampers are attached to the bottom plate. Half-slots for keeping reaction cups are formed in the main plate and the reaction cup clampers respectively in corresponding locations. After the main plate and the reaction cup clampers are assembled to the bottom plate, each facing pair of the half-slots form a holding slot which has a rectangular or square sectional shape for keeping a reaction cup. The reaction cups, once inserted into the holding slot, are clamped by the clampers. Such a solid-solid direct-heating structure has the following defects. First, it is difficult to arrange a heat source. Second, each rectangular or square holding slot is composed by two half-slots formed in the clamper and the main plate respectively, thus the structure is relatively complex.